1. Use JavaScript to write a 5-line right triangle`
<body>
<script>
for( i=0;i<5;i++){
for( j=0;j<2*i+1;j++){
document.writeln("*");
}
document.writeln("</br>")
}
</script>
</body>
2. Use JavaScript to write a 5-line isosceles triangle
<script>
for(let i=0;i<5;i++){
for(let j=5;j>i;j--){
document.writeln(" ");
}
for(let k=0;k<2*i+1;k++){
document.writeln("*")
}
document.writeln("</br>")
}
</script>
3. Use JavaScript to write a multiplication table of nine to nine
<body>
<script>
var str='';
for(var i=1;i<=9;i++){
for(var j=1;j<=i;j++){
str +=j +'*'+i+'='+i*j ;
}
str +='\n'
}
console.log(str);
</script>
</body>
Fourth, use JavaScript to write prime numbers from 1 to 100
<script>
for (var i = 2; i <= 100; i++) {
for (var j = 2; j <= i; j++) {
if (i % j == 0) {
break;
}
}
if (j >= i) {
document.write(i + ' ');
}
}
</script>